ISSN: 0378-102X
www.ucm.es\JIG
Journal of Iberian Geology 31 (2004) 135-148
The Cretaceous/Paleogene boundary at the Agost section revisited:
paleoenvironmental reconstruction and mass extinction pattern
El límite Cretácico/Paleógeno del corte de Agost revisado: reconstrucción
paleoambiental y patrón de extinción en masa
Eustoquio Molina1, Laia Alegret1,2, Ignacio Arenillas1 and José Antonio Arz1
(1)
Departamento de Ciencias de la Tierra, Facultad de Ciencias, Universidad de Zaragoza. E-50009 Zaragoza (Spain).
(2)
Department of Earth Sciences, University College London. WC1E 6BT London (United Kingdom).
[email protected], [email protected], [email protected], [email protected]
Received: 12/03/04 / Accepted: 10/06/04
Abstract
The Cretaceous/Paleogene (K/Pg) boundary event has been extensively studied in the Spanish Agost section, which contains one of
the most continuous and expanded Cretaceous-Paleogene transitions in the Tethys area. For that reason, it is considered as a classical
K/Pg boundary section, and numerous researchers have carefully analysed it from different points of view, such as micropaleontology, paleoichnology, magnetostratigraphy, mineralogy and geochemistry. Sediments from the Upper Cretaceous (Abathomphalus
mayaroensis and Plummerita hantkeninoides planktic foraminiferal Biozones), and from the lower Paleogene (Guembelitria cretacea, Parvularugoglobigerina eugubina, Parasubbotina pseudobulloides and Globanomalina compressa Biozones), correspond to a
marly, microfossil-rich sequence that was deposited in the upper and middle part of the slope, as indicated by the benthic foraminiferal assemblages. A dark clay layer containing impact evidence is identified at the base of the Danian. Planktic foraminifera show a
catastrophic mass extinction pattern in coincidence with the K/Pg, just at the base of the dark clay layer. Approximately 70% of the
species clearly became extinct at the K/Pg boundary. Very few species seem to disappear in the uppermost Maastrichtian, although
these disappearances might result from the background extinction pattern or the remaining Signor-Lipps effect. Some Cretaceous
species seem to have survived, and gradually disappear during the Danian, although this might be due to the long-term effect of
the asteroid impact; their presence in Danian sediments can be also interpreted as the result of reworking processes. If we take this
into account, the percentage of planktic foraminifera that became extinct at the K/Pg boundary makes up to 90% of the species. In
contrast to planktic foraminifera, benthic foraminifera did not suffer any mass extinction, although the drastic reorganization of their
assemblages in coincidence with the boundary reflects important environmental changes. These changes are compatible with the
castastrophic effects of a large asteroid impact that occurred just at the Cretaceous/Paleogene boundary.
Keywords: Foraminifera, extinction, paleoenvironment, Cretaceous, Paleogene, Spain.
Resumen
El evento del límite Cretácico/Paleógeno (K/Pg) ha sido intensamente estudiado en el corte español de Agost, que contiene uno de
los tránsitos Cretácico-Paleógeno más continuos y expandidos en el área del Tetis. Por este motivo, se considera como una sección
clásica del límite K/Pg, y ha sido detalladamente analizada por numerosos especialistas desde el punto de vista micropaleontológico, paleoicnológico, magnetoestratigráfico, mineralógico y geoquímico. Los sedimentos del Cretácico Superior (Biozonas de
Abathomphalus mayaroensis y de Plummerita hantkeninoides) y del Paleógeno inferior (Biozonas de Guembelitria cretacea, de
Parvularugoglobigerina eugubina y de Parasubbotina pseudobulloides) corresponden a una secuencia principalmente margosa rica
en microfósiles, depositada en la parte superior y media del talud, tal y como indican las asociaciones de foraminíferos bentónicos.
En el Daniense basal se identifica una capa arcillosa oscura que contiene evidencias de impacto. Los foraminíferos planctónicos
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muestran un patrón de extinción en masa catastrófico en coincidencia con el límite K/Pg, situado en la base de esta capa arcillosa.
El 70% de las especies se extinguieron claramente en coincidencia con en el límite K/Pg. Muy pocas especies parecen extinguirse
en el Maastrichtiense final y podrían interpretarse como parte del patrón de extinción de fondo o el remanente efecto Signor-Lipps.
Algunas especies cretácicas parecen sobrevivir el evento y desaparecer gradualmente en el Daniense, tal vez como resultado de los
efectos a más largo plazo del impacto meteorítico. Sin embargo, su presencia en el Daniense también podría ser interpretada como
resultado de la reelaboración. Teniendo en cuenta estas consideraciones, el porcentaje de especies de foraminíferos planctónicos
que se extinguieron en el evento del límite K/Pg alcanzaría el 90%. A pesar de que los foraminíferos bentónicos, al contrario que
los foraminíferos planctónicos, no sufrieron una extinción en masa, la drástica reorganización de sus asociaciones en coincidencia
con el límite refleja importantes cambios paleoambientales, compatibles con los efectos catastróficos causados por el impacto de un
asteroide justo en el límite Cretácico/Paleógeno.
Palabras clave: Foraminíferos, extinción, paleambiente, Cretácico, Paleógeno, España
1. Introduction
The Cretaceous/Paleogene boundary event has been
the object of multidisciplinary studies in the Agost section, which is one of the most relevant and best-known
Spanish Cretaceous/Paleogene (K/Pg) boundary sections. Since the proposal of the impact theory (Alvarez
et al., 1980; Smit and Hertogen, 1980), the Spanish
sections of Caravaca and Agost became classical localities to test the impact evidence and the mass extinction
pattern. The Agost section was first described by Leclerc
(1971), who investigated the planktic foraminiferal faunas and argued that the sedimentation in this section was
essentially continuous from Santonian to Eocene. Since
then, the Agost section has been studied by numerous
authors (e.g., von Hillebrandt, 1974; Groot et al., 1989;
Smit, 1990; Canudo et al., 1991; Martínez-Ruiz et al.,
1992, 1997; Ortega-Huertas et al., 1995, 1998; Molina et
al., 1996, 2001; Pardo et al., 1996; Arenillas, 2000; Arz,
2000; Alegret, 2003; Alegret et al., 2003), who analysed
the micropaleontology, paleoichnology, biostratigraphy,
magnetostratigraphy, mineralogy and geochemistry. Finally, a field trip was organized (Molina et al., 2003) during the meeting Bioevents: their stratigraphical records,
patterns and causes, organized in Caravaca de la Cruz,
June 3rd-8th, 2003.
The aim of this paper is to update and integrate the data
that have been published on the Upper Cretaceous and
lower Paleogene from Agost, especially those related to
foraminifera, in order to reconstruct the paleoenvironment and to evaluate the magnitude of the catastrophic
mass extinction.
2. Location and Stratigraphy
The Agost section is located in the Betic Cordillera of
southeastern Spain and the outcrop occurs about 1 km
north of the village of Agost, in Alicante province (Fig.
1). Agost is located ~100 km to the east of the well-
Fig. 1.- Geologic setting, and geographic location of the Agost section.
Fig. 1.- Localización geológica y geográfica del corte de Agost.
known Caravaca section; both sections have a similar
lithology and have been considered as some of the most
continuous land-based K/Pg sections. The Cretaceous/
Paleogene transition is well exposed, and can be easily
sampled along a road cut near the 13 km-marker post of
the Agost-Castalla road (Fig. 2).
Upper Cretaceous and lower Paleogene sediments
at Agost include the upper part of the Cenomanian to
the Eocene Quipar-Jorquera Formation (Vera, 1983),
which was originally described by Van Veen (1969).
Maastrichtian sediments consist of gray pelagic, massive marls, interbedded with marly limestones; the latter
are very scarce in the uppermost Maastrichtian. These
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
137
Fig. 2.- General view of the uppermost Cretaceous and lower Paleogene at the Agost section (above); detail of the lower Danian dark clay layer
(left); and detail of the red rusty layer at the K/Pg boundary (right).
Fig. 2.- Vista general del Cretácico terminal y del Paleógeno inferior en el corte de Agost (arriba); detalle de la arcilla oscura del Daniense inferior
(izquierda); detalle del nivel rojizo del límite K/Pg (derecha).
marly sediments are rich in foraminifera, ostracods and
other microfossils (see field trip guides by Usera et al.
2000; Molina et al. 2001; 2003). The K/Pg boundary is
marked by a sharp contact between the Maastrichtian
marly sediments and a 12 cm-thick layer of black clays,
with a 2-3 mm thick, red ferruginous level at its base. The
ferruginous level contains goethite, hematite, glauconitic
clasts, scarce foraminifers, and is enriched in Ir, Ni-rich
spinels, Co, Cr as well as sanidine spherules that Smit
(1982, 1990) interpreted to be altered microtektites. This
oxidized level has been called the “fall-out layer”, which
marks the K/Pg boundary (Smit, 1982, 1990; Canudo et
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al., 1991; Arz et al., 1992; Martínez Ruiz et al., 1992,
1999; Molina et al., 1996; Alegret et al., 2003). A detailed magnetostratigraphic analysis of the Agost section
across the K/Pg boundary was performed by Groot et al.
(1989). They identified the polarity zones C30n, C29r
and C29n. The K/Pg boundary is placed at two-thirds
from the base of chron C29r. The correlation between
this magnetostratigraphy and the planktic foraminiferal
biostratigraphy was commented by Berggren (1989) and
analysed by Arenillas et al. (1993). Figure 3 shows a correlation of planktic foraminiferal biozonations and the
magnetostratigraphy at Agost.
The lowermost Danian dark clay level is overlain by
a 10 cm-thick layer of massive gray clays. Higher in
the section, we recognised two decimeter-thick tabular
bodies of marly limestones, with a decimeter-thick intercalated layer of marls. The upper part of the section consists mainly of massive gray marls, with a 10 cm-thick
body of marly limestones intercalated 230 cm above
the K/Pg boundary. Trace fossils are frequent across the
K/Pg boundary. Paleoichnological approach has been
performed by analysing ichnotaxa, relative abundance,
horizontal and vertical distribution of trace fossils, and
cross-cutting relantionship (Rodríguez-Tovar in Molina
et al., 2001; Rodríguez-Tovar et al., 2004).
3. Mineralogy and Geochemistry
The K/Pg boundary layer at Agost is characterized by
a sharp decrease in carbonate content and a subsequent
increase in the proportion of clays. Smectite and diagenetically altered spherules made up of either potassium
feldspar or iron oxides are the main components of the
boundary layer (Smit, 1990; Martínez-Ruiz et al., 1992,
1997; Ortega-Huertas et al., 1995, 1998). Other trace
minerals such as celestite, barite, rutile, Cr oxides, chlorite and palygorskite are also observed in the boundary
layer, and in the dark marly clays deposited above this
layer.
As in other K/Pg boundary sections worldwide, the K/
Pg boundary at Agost is marked by significant geochemical anomalies characterized by a large increase of Ir and
other platinum group elements. The boundary is also
marked by high contents of different chemical elements
such as Fe, Cr, Co, Ni, Cu, Zn, As or Sb and significant
changes in δ13C and δ18O (Smit, 1990, Martínez-Ruiz et
al., 1992, 1994, 1999). The geochemical composition of
the boundary layer at Agost and the enrichment in typical
extraterrestrial elements thus support the impact scenario
at the end of the Cretaceous. In addition, trace element
data from the dark clay layer at the base of the Danian
indicate that anoxic to hypoxic conditions occurred either
at the botton or in the pore waters. Hypoxic conditions
appear to have been somewhat more extreme at Agost
than at Caravaca (Martínez-Ruiz et al., 1992; 1999;
Kaiho and Lamolda, 1999).
4. Planktic foraminifera
4.1. Biostratigraphy
The planktic foraminiferal biostratigraphy of the Upper
Cretaceous and lower Paleogene transition from Agost
was studied by Molina et al. (1996; 1998), who suggested
that the stratigraphic ranges are very similar to those of
the Caravaca section in Spain, and the El Kef section in
Tunisia. These authors used the classical system of biozonation to identify six biozones across the K/Pg interval
at Agost, namely Abathomphalus mayaroensis Biozone,
Plummerita hantkeninoides Biozone, Guembelitria
cretacea Biozone, Parvularugoglobigerina eugubina
Biozone, Parasubbotina pseudobulloides Biozone and
Globanomalina compressa Biozone. Recently, a new
high-resolution planktic foraminiferal zonation and subzonation for the lower Danian has been established based
on some of the most expanded and continuous pelagic
sections including Agost (Arenillas et al., 2004). The
zones and subzones (Fig. 3) are defined as follows:
-Abathomphalus mayaroensis Zone: Biostratigraphical
interval between the lowest record datum (LRD) of the
nominal taxon and the HRD of Plummerita hantkeninoides. This biozone was divided in three subzones by
Arz and Molina (2002), but at the Agost section only the
uppermost one has been studied: Plummerita hantkeninoides Subzone, which is the biostratigraphical interval
characterized by the total range of the nominal taxon. At
the Agost section, the total range of P. hantkeninoides
spans the top 3.45 m of the Maastrichtian.
-Guembelitria cretacea Zone: Biostratigraphical interval between the highest record datum (HRD) of Plummerita hantkeninoides, precisely at the K/Pg boundary,
and the LRD of Parvularugoglobigerina eugubina. In
the Agost section the G. cretacea Biozone spans 14 cm
within the level that is mainly characterised by black
clays containing a well-preserved autochthonous fauna.
The first Tertiary planktic foraminiferal species are found
in the lower part of this biozone, which is the stratigraphical interval equivalent to the Zone P0 of Berggren et al.
(1995). This biozone was divided in two by Arenillas et
al. (2004): Hedbergella holmdelensis Subzone, which
is the biostratigraphical interval between the HRD of
Plummerita hantkeninoides to the LRD of Parvularugoglobigerina longiapertura; and Parvularugoglobigerina
longiapertura Subzone, which is the biostratigraphical
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
139
Fig. 3.- Magnetostratigraphy, and planktic foraminiferal biostratigraphy at Agost. The biozonation used in this paper is based on Arz and Molina
(2002) for the Upper Cretaceous, and Arenillas et al. (2004) for the Paleocene.
Fig. 3.- Magnetoestratigrafía y bioestratigrafía con foraminíferos planctónicos en Agost. La biozonación utilizada en este trabajo está basada en
Arz y Molina (2002) para el Cretácico Superior y en Arenillas et al. (2004) para el Paleoceno.
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interval from the LRD of the nominal taxon and the LRD
of Parvularugoglobigerina eugubina.
- Parvularugoglobigerina eugubina Zone: Biostratigraphical interval between the LRD of the nominate
taxon and the LRD of Parasubbotina pseudobulloides.
The Pv. eugubina Biozone is 45 cm thick at Agost. This
biozone was divided in two by Arenillas et al. (2004):
Parvularugoglobigerina sabina Subzone, which is the
interval ranging from the LRD of Parvularugoglobigerina eugubina to the LRD of Eoglobigerina simplicissima;
and Eoglobigerina simplicissima Subzone, which is the
interval between the LRD of the nominal taxon and the
LRD of Parasubbotina pseudobulloides.
- Parasubbotina pseudobulloides Zone: Biostratigraphical interval between the LRD of the nominal taxon and
LRD of Globanomalina compressa. This biozone spans
3.70 m at Agost. This biozone was divided in two by
Arenillas et al. (2004): Eoglobigerina trivialis Subzone,
which is the biostratigraphical interval from the LRD of
Parasubbotina pseudobulloides to the LRD of Subbotina
triloculinoides; and Subbotina triloculinoides Subzone,
which is the interval from the LRD of the nominal taxon
to the LRD of Globanomalina compressa.
- Globanomalina compressa Biozone: Biostratigraphical interval between the LRD of the nominal taxon
and the LRD of Acarinina trinidadensis. At Agost, this
biozone spans 6 m.
4.2. Planktic foraminiferal turnover
The Agost section has been very relevant to solve the
controversy generated since the proposal of a model explaining the planktic foraminiferal mass extinction at the
K/Pg boundary. Such a controversy originated in 1981,
at the Snowbird I Conference, where Jan Smit presented
his data showing that all but one Cretaceous species suddenly became extinct at the K/Pg boundary. He interpreted this dramatic faunal turnover as the result of a large
asteroid impact (Smit and Hertogen, 1980; Smit, 1982).
Afterwards, these data were questioned by Gerta Keller,
who argued that species extinctions extended across the
K/Pg boundary with about 1/3 of the species surviving
well into the Tertiary (Keller, 1988, 1989a,b). Nevertheless, most recent studies (Molina et al., 1998; Arz et al.,
1999; Arenillas et al., 2000 a,b, among others) showed
a sudden and catastrophic pattern of extinction that they
also believed is compatible with a large asteroid impact,
as initially proposed by Smit and Hertogen (1980) and
Alvarez et al. (1980).
In order to elucidate this controversy, Molina et al.
(1996) studied the Agost section, which is very expanded
and continuous, and well exposed across the K/Pg bound-
ary. A total of 68 samples were collected at cm-intervals
across the critical K/Pg boundary interval and at m-intervals well below and above the boundary. Planktic
foraminifera are well preserved, the assemblages are rich
and diverse and there is almost no evidence of reworking.
Thus, this excellent K/Pg boundary section provided a
good opportunity to test the extinction model of Cretaceous species and the evolution of Tertiary species.
Upper Maastrichtian assemblages from the Agost section are largely dominated by short life-cycle biserial species such as heterohelicids. Planispiral (globigerinelloids)
and trochospiral (hedbergellids, rugoglobigerinids and
globotruncanids) species are frequent, and triserial species (guembelitriids) and tubulospinose species (schackoinids) are rare. The stratigraphic ranges of these taxa
during the late Maastrichtian indicate very few changes
in the faunal assemblages, and most of the species are
present in the A. mayaroensis Zone. The HRDs of some
species, such as Gansserina wiedenmayeri, Gansserina
gansseri and Contusotruncana plicata, are placed in the
upper Maastrichtian A. mayaroensis Biozone between 6
and 11 m below the K/Pg boundary. The HRDs of the rest
of the species (Rugoglobigerina milamensis, Archaeoglobigerina cretacea, Gublerina acuta and Rugoglobigerina
pennyi) are placed in the upper part of the P. hantkeninoides Subzone (Fig. 4). Only one species, namely P.
hantkeninoides, has its LRD in this interval at 3.45 m below the K/Pg boundary. Quantitative planktic foraminiferal analysis of the uppermost 2.25 m of the Cretaceous
shows little variation among the relative abundances of
the different species (Fig. 3 in Molina et al., 1996).
A total of 46 species have their highest record in coincidence with the red rusty layer that marks the K/Pg boundary. We double-checked this coincidence by scanning the
residue of the uppermost Cretaceous samples twice, in
order to minimize the Signor-Lipps effect (Signor and
Lipps, 1982), because certain rare species might seem to
go extinct before their real moment of extinction (Canudo
et al. 1991). About 72% of the planktic foraminiferal species became extinct in coincidence with the K/Pg boundary, which constitutes the most important extinction
event in the history of planktic foraminifera. Most of the
extinct taxa, as for instance Contusotruncana contusa,
Globotruncana arca, Abathomphalus mayaroensis, are
large, complex forms adapted to deep environments.
In order to eliminate the potential problem of reworking in a high-resolution sampling, Molina et al. (1996,
1998, 2001, 2003) ignored either the presence of isolated
specimens in a sample, or specimens with a different
preservation. Such specimens were assumed to have been
reworked, and hence were not listed in their data tables or
figures. In the lowermost Paleogene (G. cretacea, Pv. eu-
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
141
Fig. 4.- Planktic foraminiferal ranges across the Cretaceous-Paleogene transition at Agost.
Fig. 4.- Distribución de los foraminíferos planctónicos a través del tránsito Cretácico-Paleógeno en Agost.
gubina, Ps. pseudobulloides Biozones and the lower part
of G. compressa Biozone), a total of 14 Cretaceous species were identified that may be considered as possible
Cretaceous survivors, or as reworked specimens (Kaiho
and Lamolda, 1999). These species are cosmopolitan,
small and simple surface dwellers that apparently disappeared during the lowermost Danian (Fig. 4). Guembelitriids (Guembelitria trifolia and G. cretacea) are rare in
the Upper Cretaceous, but these opportunistic species are
abundant in the lowermost Paleogene, just after the main
planktic foraminiferal extinction event. The rest of the
small Cretaceous possible survivors are less abundant in
the Danian than in the Maastrichtian, thus indicating the
possibility of reworking.
The biostratigraphical data at Agost indicate that new
opportunistic cosmopolitan species evolved in the earliest Danian and two main Danian assemblages are recognised. The earliest assemblage consists of small cos-
mopolitan surface dwellers, which originated in the G.
cretacea Biochron, and became extinct in the early part of
the Ps. pseudobulloides Biochron. The second assemblage
originated in the Pv. eugubina Biochron, and diversified
within the early part of the Ps. pseudobulloides Biochron,
where these taxa reached a normal size (200-300 µm).
Species that dominated the lower Danian assemblages
are those which evolved after the K/Pg boundary, and
most of them became extinct near the base of the Ps.
pseudobulloides Biochron (e.g., Parvularugoglobigerina
longiapertura, Pv. eugubina, Pv. sabina, Globoconusa
fodina and G. alticonusa). Subsequent to their disappearance, Woodringina claytonensis, Woodringina hornerstownensis, Chiloguembelina morsei and Chiloguembelina midwayensis dominated the assemblages (Fig. 4).
In conclusion, the Agost section shows evidence for a
catastrophic mass extinction of about 72% of the Cretaceous species of planktic foraminifera that exactly
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coincides with the base of the red rusty layer containing clues of an impact event. This is similar to what is
found in Tunisia and other K/Pg sections (Molina et al.,
1996; 1998; Arz and Arenillas, 1998; Arenillas et al.,
2000b). The few species that seem to disappear in the
uppermost Maastrichtian can be interpreted to constitute
background extinction pattern, or can also be interpreted
as the remaining Signor-Lipps effect. Species that seem
to disappear in the lowermost Danian may either be the
result of the long-term effect of the asteroid impact, or
may be reworked (Kaiho and Lamolda, 1999). Only few
species such as Guembelitria cretacea, Guembelitria
trifolia, probably Hedbergella monmouthensis, Hedbergella holmdelensi,s and possibly Heterohelix globulosa
and Heterohelix navarroensis, should be considered as
survivors. We suggest that the pattern of extinction and
origination is very compatible with the impact theory,
which caused the extinction of about 90% of the species
of planktic foraminifera across the K-Pg transition.
5. Benthic foraminifera
Benthic foraminifera are an important source of information about paleoenvironmental conditions at the sea
floor, such as ocean productivity and oxygenation. In addition to being excellent paleobathymetric markers, the
abundance of some depth-related species, as well as the
upper depth-limits of others, allow us to infer possible
changes in paleodepth.
So far, studies of the upper Maastrichtian through lower
Danian benthic foraminifera from Southeastern Spain are
scarce, and they consist only of brief descriptions of the
benthic foraminiferal faunas from Caravaca (Smit, 1990;
Keller, 1992; Coccioni et al., 1993; Coccioni and Galeotti, 1994; Widmark and Speijer, 1997a, b), and Agost
(Pardo et al., 1996). More recently, Alegret et al. (2003)
performed a detailed quantitative analysis of the Upper
Cretaceous and lower Paleogene benthic foraminiferal
assemblages from Agost, and inferred paleoenvironmental
and paleobathymetrical changes across the K-Pg transition;
their main results are discussed in the following paragraphs.
ifera at Agost in terms of climatic changes and variations
in sea level. They also concluded that paleodepths fluctuated between upper bathyal and outer neritic. In contrast,
Alegret et al. (2003) recently developed a detailed paleobathymetric reconstruction of the Upper Cretaceous and
Lower Paleogene sediments at Agost and concluded that
benthic foraminiferal assemblages from the A. mayaroensis and lower part of the P. hantkeninoides Biozones,
which contain abundant Loxostomum eleyi, Eouvigerina
subsculptura, laevidentalinids, Sitella cushmani, Spiroplectammina spectabilis, and Stensioeina beccariiformis
forma parvula, indicate an uppermost bathyal depth of
deposition (Fig. 5). They further observed a decrease in
the percentage of Loxostomum eleyi in the middle part of
the P. hantkeninoides Subzone, as well as an increase in
the relative abundance of species typical of middle bathyal environments in the Tethys area, such as Bolivinoides
draco, Bolivinoides delicatulus, Cibicidoides hyphalus,
Cibicidoides velascoensis, Eouvigerina subsculptura,
Gaudryina pyramidata, Praebulimina reussi, Pseudouvigerina plummerae, Pyramidina rudita. There is also
simultaneous increase in the percentage of bathyal and
abyssal species, namely Bulimina trinitatensis, Clavulinoides trilatera, Nuttallinella florealis, Paralabamina
lunata and Stensioeina beccariiformis s.s. The composition of the assemblages thus allowed Alegret et al. (2003)
to conclude that paleodepths increased to middle bathyal
during the middle part of the P. hantkeninoides Biochron,
and remained unchanged through the rest of the section
(through the Ps. pseudobulloides Biochron; Fig. 5).
These authors did not report any perceivable bathymetrical changes at the K/Pg boundary.
A comparison between paleodepth interpretations proposed by Pardo et al. (1996) and Alegret et al. (2003) is
shown in Figure 5. According to the later authors, differences between these paleodepth curves may be due to
misidentification of several benthic foraminiferal species
by Pardo et al. (1996), as well as to their confusing usage
of the upper depth limits of certain taxa whose bathymetric distribution is well-known and broadly documented.
5.1. Paleobathymetry
5.2. Benthic foraminiferal turnover and paleoenvironmental inferences
The distribution of benthic foraminifera is related to
several depth-related parameters, therefore this group
can be used as an excellent tool to infer paleobathymetry.
Paleodepths indicated by the benthic foraminiferal faunas
are clearly of great importance to interpret the environment of deposition of the K/Pg sediments.
Pardo et al. (1996) interpreted the faunal turnover of
Upper Cretaceous and lower Paleogene benthic foramin-
Benthic foraminifera from the Upper Cretaceous and
lower Paleogene at Agost were included in the study by
Pardo et al. (1996), who observed a lack of severe extinctions and suggested that climatic changes and variations
in sea level can explain the observed faunal changes.
The K/Pg boundary marks one of the largest mass
extinctions of the Phanerozoic, but survival rates of different groups of marine organisms varied with habitat
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
Fig. 5.- Comparison between paleodepth curves inferred by Alegret
et al. (2003) and Pardo et al. (1996). Modified from Alegret et al.
(2003).
Fig. 5.- Comparación entre curvas de paleoprofundidad inferidas por
Alegret et al. (2003) y Pardo et al. (1996). Modificado de Alegret
et al. (2003).
(Peryt et al., 2002). Planktic foraminifera suffered a catastrophic mass extinction (e.g., Arenillas et al., 2000 a,b),
whereas benthic foraminiferal assemblages exhibit various degrees of faunal restructuring even in the absence of
major extinction (e.g., Alegret et al., 2003).
Upper Maastrichtian benthic foraminiferal assemblages from Agost are dominated by calcareous foraminifera
(~80%) with tapered tests, such as Loxostomum eleyi,
laevidentalinids and Eouvigerina subsculptura. The upper half of the P. hantkeninoides Biozone is dominated
by different tapered species such as Praebulimina reussi,
Spiroplectammina spectabilis and laevidentalinids (Fig.
6). According to the model proposed by Jorissen et al.
(1995), which explains benthic foraminiferal microhabitat preferences in terms of nutrient supply to the sea floor,
143
Alegret et al. (2003) interpreted these infaunal-dominated Upper Cretaceous faunas as indicating a moderately
eutrophic environment, with a food flux to the sea floor
sufficient to sustain infaunal taxa.
Only 5% of the benthic foraminiferal species became
extinct at the K/Pg boundary at Agost, although the
benthic assemblages underwent a temporary faunal turnover that started just at the boundary. The abundance of
benthic foraminifera is low in the lowermost part of the
black-clay layer at Agost (46 specimens in the first sample of the Danian, in contrast to 268 specimens found in
the uppermost Maastrichtian), and dissolution may have
affected the faunas -probably due to a temporal rise of the
lysocline-, leading to relatively high abundances (up to
48%) of agglutinated taxa.
Several peaks in relative abundance of Ammodiscus,
Glomospirella grzybowski, Repmanina charoides or Haplophragmoides, were identified in the lowermost Danian
black clay interval; these taxa have been documented
to be opportunistic species that tolerate environmental
instability and/or low oxygenation, blooming whenever
other taxa cannot compete (e.g., Kaminski et al., 1996;
Kuhnt et al., 1996; Alegret et al., 2003).
The percentage of infaunal morphogroups decreased
in coincidence with the K/Pg boundary, and Danian assemblages were dominated by epifaunal (Stensioeina
beccariiformis, Globorotalites spp., Cibicidoides hyphalus, Cibicidoides ekblomi) or mixed epifaunal-infaunal
morphogroups. Such a decrease in the percentage of
infaunal morphogroups suggests that the food supply to
the benthos drastically decreased in coincidence with the
K/Pg boundary, and that the scarce organic matter was
consumed at or close to the sediment surface before it
could be buried in the sediment, so that no food remained
for deep-infaunal taxa (e.g., Peryt et al., 2002).
Alegret et al. (2003) argued that the strong variability
in the fauna, as well as the low diversity and abundance
of benthic foraminifera during the first 10-15 kyr (lower
∼10 cm) of the Danian reflects not just a collapse of the
food supply, but also a major change in the composition
of the food supply as a result of the mass extinction of
phytoplankton, as well as a rapidly changing food supply driven by blooms of such taxa as Thoracosphaera,
Braarudosphaera or Biscutum (e.g., Thierstein, 1981;
Perch-Nielsen et al., 1982).
Increase in genus richness and in diversity of the assemblages (Alegret, 2003), and decrease in the percentage of
opportunistic taxa at the end of the G. cretacea Biochron,
indicate a slight stabilization of the ecosystems. Nevertheless, the high percentage of epifaunal morphogroups
(e.g., Cibicidoides ekblomi, Cibicidoides hyphalus, Globorotalites sp., Stensioeina beccariiformis) towards the
144
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
Fig. 6.- Dominant upper Maastrichtian to lower Danian benthic foraminiferal taxa at Agost.
Fig. 6.- Taxones de foraminíferos bentónicos dominantes durante el
Maastrichtiense superior y Daniense inferior en Agost.
top of the interval studied suggests that productivity did
not recover to pre-extinction levels at Agost, at least in
the interval of the Ps. pseudobulloides Biozone that has
been investigated.
6. Conclusions
The classical K/Pg boundary Agost section has been
revisited and analysed mainly from the micropaleontological point of view. The expanded and well-exposed
Upper Cretaceous to lower Paleogene sequence contains
well preserved benthic and planktic foraminiferal assemblages, which allowed us to perform very detailed
biostratigraphical, paleobathymetrical and paleoenvironmental analyses.
Benthic foraminifera at Agost indicate deposition at
uppermost bathyal depths during the A. mayaroensis
Biozone through the early P. hantkeninoides Biozone.
Paleodepths increased to middle bathyal for the remainder of the time interval studied in the section, and no
paleobathymetrical changes have been observed in coincidence with the K/Pg boundary.
Planktic foraminifera show a catastrophic mass extinction pattern in coincidence with the layer containing
evidence for an asteroid impact, and about 70% of the
species clearly became extinct at the K/Pg boundary.
The few species that seem to disappear in the uppermost
Maastrichtian may constitute background extinction pattern, or they could also be interpreted as the remaining
Signor-Lipps effect. Species that seem to disappear in the
lowermost Danian could be the result of the long-term
effect of the asteroid impact. On the other hand, these
delayed extinctions could also be interpreted as due to
reworking, and only few species such as Guembelitria
cretacea, Guembelitria trifolia, probably Hedbergella
monmouthensis, Hedbergella holmdelensis and possibly
Heterohelix globulosa and Heterohelix navarroensis
should be considered as survivors.
On the whole, the magnitude of the catastrophic mass
extinction pattern in planktic foraminifera could be as
high as about 90%. In contrast, benthic foraminifera did
not suffer mass extinction, indicating that the benthic environment was less affected than the planktic one. However, benthic assemblages indicate a drastic decrease in
nutrient supply to the sea floor in coincidence with the K/
Pg boundary, followed by environmental instability and/
or low oxygenation during the lowermost Danian and a
slow recovery through the lower Danian. The benthic foraminiferal changes and the inferred paleoenvironmental
turnover are also very compatible with the castastrophic
effect caused by a large asteroid that impacted at Chicxulub (Yucatan Peninsula) at the K/Pg boundary.
7. Acknowledgements
This research was funded by DGES project BTE20011809 of the Spanish Ministerio de Ciencia y Tecnología
and by DGA group and project P131/2001 of the Aragonian Departamento de Educación y Ciencia. L. Alegret
thanks the Spanish Ministerio de Educación, Cultura y
Deporte for the postdoctoral grant EX2003-0007. We are
grateful to Florentin J-M.R. Maurrasse and Marcos A.
Lamolda for their valuable comments.
8. References
Alegret, L. (2003): Sedimentología y Micropaleontología
(foraminíferos bentónicos) del tránsito Cretácico-Terciario:
correlación entre las áreas del Golfo de México y del Tethys.
Tesis Doctoral, Universidad de Zaragoza. Bell Howell Ed.,
Nº publ. 3073947, 476 pp.
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
Alegret, L, Molina, E., Thomas, E. (2003): Benthic foraminiferal turnover across the Cretaceous/Paleogene boundary at
Agost (southeastern Spain): paleoenvironmental inferences.
Marine Micropaleontology, 48: 251-279.
Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V. (1980):
Extraterrestrial cause for the Cretaceous-Tertiary extinction.
Science, 208: 1095-1108.
Arenillas, I. (2000): Los foraminíferos planctónicos del Paleoceno-Eoceno Inferior: Sistemática, Bioestratigrafía,
Cronoestratigrafía y Paleoceanografía. Tesis Doctoral, 513
p. Prensas Universitarias de Zaragoza.
Arenillas, I., Arz, J.A., Molina, E., Dupuis, Ch. (2000a): An
independent test of planktic foraminiferal turnover across
the Cretaceous/Paleogene (K/P) boundary at El Kef, Tunisia:
catastrophic mass extinction and possible survivorship. Micropaleontology, 46 (1): 31-49.
Arenillas, I., Arz, J.A., Molina, E. (2004): A new high-resolution planktic foraminiferal zonation and subzonation for the
lower Danian. Lethaia, 37: 79-95.
Arenillas, I., Arz, J.A., Molina, E., Dupuis, Ch. (2000b):
The Cretaceous/Tertiary boundary at Aïn Settara, Tunisia: sudden catastrophic mass extinction in planktic
foraminifera. Journal of Foraminiferal Research, 30 (2):
202-218.
Arenillas, I., Canudo, J.I., Molina, E. (1993): Correlación entre
la magnetoestratigrafía y la Bioestratigrafía con foraminíferos planctónicos del Paleoceno Inferior en Agost (Béticas) y
Zumaya (Pirineos). Comunicaciones de las IX Jornadas de
Paleontología, Málaga, 1-6.
Arz, J.A. (2000): Los foraminíferos planctónicos del Campaniense y Maastrichtiense: Bioestratigrafía, Cronoestratigrafía
y eventos paleoecológicos. Tesis Doctoral. 419 p. Prensas
Universitarias de Zaragoza.
Arz, J.A., Arenillas, I. (1998): Foraminíferos planctónicos del
tránsito Cretácico-Terciario del Pirineo occidental (España):
Bioestratigrafía, análisis cuantitativo y Tafonomía. Revista
de la Sociedad Mexicana de Paleontología, (2): 146-162.
Arz J.A., Canudo J.I., Molina, E. (1992): Estudio comparativo
del Maastrichtiense de Zumaya (Pirineos) y Agost (Béticas)
basado en el análisis cuantitativo de los foraminíferos planctónicos. Actas III Congreso Geológico de España, Salamanca, 1: 487-491.
Arz, J.A., Arenillas, I., Molina, E., Dupuis, Ch. (1999): Los
efectos tafonómico y “Signor-Lipps” sobre la extinción en
masa de foraminíferos planctónicos en el límite Cretácico/
Terciario de Elles (Tunicia). Revista de la Sociedad Geológica de España, 12 (2): 251-267.
Arz, J.A., Molina, E. (2002). Bioestratigrafía y cronoestratigrafía con foraminíferos planctónicos del Campaniense superior y Maastrichtiense de latitudes templadas y subtropicales
(España, Francia, Tunicia). Neues Jarbuch fur Geologie und
Paläontologie, Abhanlungen, 224(2): 161-195.
Berggren, W.A. (1989). Comments on the paper “Magnetostratigraphy of the Cretaceous-Tertiary boundary at Agost
(Spain)” by J.J. Groot, R.B.G. de Jonge, C.G. Langereis,
W.G.H.Z. ten Kate and J. Smit. Earth and Planetary Science
Letters, 95: 183-185.
145
Berggren, W.A., Kent, D.V., Swisher, C.C., Aubry, M.A.
(1995): A revised Paleogene geochronology and chronostratigraphy. In W.A. Berggren, Kent, D.V., Hardenbol, J.
(eds). Geochronology, time scales and global stratigraphic
correlation. SEPM Special Publication, 54: 129-212, Tulsa,
Oklahoma.
Canudo, J.I., Keller, G., Molina, E. (1991): Cretaceous/Tertiary
boundary extinction pattern and faunal turnover at Agost and
Caravaca, S.E. Spain. Marine Micropaleontology, 17: 319-341.
Coccioni, R., Fabbrucci, L., Galeotti, S. (1993): Terminal
Cretaceous deep-water benthic foraminiferal decimation,
survivorship and recovery at Caravaca (SE Spain). Palaeopelagos, 3: 3-24.
Coccioni, R., Galeotti, S. (1994): K-T boundary extinction:
geologically instantaneous or gradual event? Evidence from
deep-sea benthic foraminifera. Geology, 22: 779-782.
Groot, J.J., De Jonge, R.B.G., Langereis, C.G., Ten Kate,
W.G.H.Z., Smit, J. (1989): Magnetostratigraphy of the
Cretaceous-Tertiary boundary at Agost (Spain). Earth and
Planetary Science Letters, 94: 385-397.
Jorissen, F.J., de Stigter, H.C., Widmark, J.G.V. (1995): A conceptual model explaining benthic foraminiferal microhabitats: Marine Micropaleontology, 26: 3-15.
Kaiho, K., Lamolda, M. (1999): Catastrophic extinction of
planktonic foraminfera at the Cretaceous-Tertiary boundary
evidenced by stable isotopes and foraminiferal abundance at
Caravaca, Spain. Geology, 27(4): 355-358.
Kaminski, M.A., Kuhnt, W., Radley, J.D. (1996): PaleoceneEocene deep water agglutinated foraminifera from the Numidian Flysch (Rif, Northern Morocco): their significance
for the paleoceanography of the Gibraltar gateway. Journal
of Micropaleontology, 15: 1-19.
Keller, G. (1988): Extinction, survivorship and evolution of
planktic foraminifers across the Cretaceous/Tertiary boundary
at El Kef, Tunisia. Marine Micropaleontology, 13: 239-263.
Keller, G. (1989a): Extended period of extinctions across the
Cretaceous/Tertiary boundary in planktonic foraminifera
of continental shelf sections: Implications for impact and
volcanism theories. Geological Society of America Bulletin,
101: 1408-1419.
Keller, G. (1989b): Extended Cretaceous/Tertiary boundary
extinctions and delayed population change in planktonic
foraminiferal faunas from Brazos River, Texas. Paleoceanography, 4: 287-332.
Keller, G. (1992): Paleoecologic response of Tethyan benthic
foraminifera to the Cretaceous-Tertiary boundary transition.
In: Takayanagi, Y., Saito, T. (Eds.), Studies in Benthic Foraminifera. Tokai University Press, 77-91, Tokyo.
Kuhnt, W., Moullade, M., Kaminski, M.A. (1996): Ecological
structuring and evolution of deep sea agglutinated foraminifera- a review. Revue de Micropaléontologie, 39: 271-281.
Leclerc, J. (1971): Etude géologique du massif du Maigmó et
de ses abords. Doctoral Thesis, Géologie Structural, 96-100.
Martínez-Ruiz, F., Ortega-Huertas, M., Palomo, I., Barbieri,
M. (1992): The geochemistry and mineralogy of the Cretaceous-Tertiary boundary at Agost (southeast Spain). Chemical Geology, 95: 265-281.
146
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
Martínez-Ruiz, F., Ortega-Huertas, M., Palomo, I. (1994): The
Cretaceous/Tertiary boundary in the Betic Cordilleras and
Basque-Cantabrian basin: a comparative study of the platinum-group elements anomalies. Mineralogical Magazine,
58: 463-564.
Martínez-Ruiz, F., Ortega-Huertas, M., Palomo, I. (1999):
Positive Eu anomaly development during diagenesis of the
K/T boundary ejecta layer in the Agost section (SE Spain):
implications for trace-element removilization. Terra Nova,
11: 290-296.
Martínez-Ruiz, F., Ortega-Huertas, M., Palomo, I., Acquafredda, P. (1997): Quench textures in altered spherules from the
Cretaceous-Tertiary boundary layer at Agost and Caravaca,
SE Spain. Sedimentary Geology, 113: 137-157.
Molina, E., Arenillas, I., Arz, J.A. (1996): The Cretaceous/
Tertiary boundary mass extinction in planktic foraminifera
at Agost, Spain. Revue de Micropaléontologie, 39 (3), 225243.
Molina, E., Arenillas, I., Arz, J.A. (1998): Mass extinction in
planktic foraminifera at the Cretaceous/Tertiary boundary in
subtropical and temperate latitudes. Bulletin de la Société
géologique de France, 169(3): 351-363.
Molina, E., Alegret, L., Arenillas, I., Arz, J.A., Gonzalvo,
C., Martínez-Ruiz, F, Ortega-Huertas, M., Palomo, I., Rodríguez-Tovar, F. (2001): Field-trip guide to the Agost and
Caravaca sections (Betic Cordillera, Spain). ESF-IMPACT
6th Workshop, 72 p. Granada.
Molina, E., Alegret, L., Arenillas, I., Arz, J.A. (2003): The
Cretaceous/Tertiary boundary at the Agost section (Alicante
Province, Betic Cordillera). Field-trip guide, Bioevents Caravaca 2003, 1-13.
Ortega-Huertas, M., Martínez-Ruiz, F., Palomo, I., Chanley,
H. (1995): Comparative mineralogical and geochemical
clay sedimentation in the Betic Cordilleras and BasqueCantabrian Basin areas at the Cretaceous-Tertiary boundary.
Sedimentary Geology, 94: 209-227.
Ortega-Huertas, M., Martínez-Ruiz, F., Palomo, I., González, I.
(1998): Geological factors controlling clay mineral patterns
across the Cretaceous-Tertiary boundary in Mediterranean
and Atlantic sections. Clay Minerals, 33: 483-500.
Pardo, A., Keller, G., Ortiz, N. (1996): Latest Maastrichtian
and K/T boundary foraminiferal turnover and environmental
changes at Agost, Spain. In: N. MacLeod, G. Keller (eds),
Cretaceous-Tertiary Mass Extinctions: Biotic and Enviromental Changes, 139-171, Norton and Company, New
York.
Perch-Nielsen, K., McKenzie, J., He, Q. (1982): Biostratigraphy and isotope stratigraphy and the ‘catastrophic’ extinction of calcareous nannoplankton at the Cretaceous/Tertiary
boundary. Geological Society of America Specical Paper,
190: 353-371.
Peryt, D., Alegret, L., Molina, E. (2002): The Cretaceous/
Paleogene (K/P) boundary at Aïn Settara, Tunisia: restructuring of benthic foraminiferal assemblages. Terra Nova, 14:
101-107.
Rodríguez-Tovar, F. J., Martínez-Ruiz, F., Bernasconi, S.
(2004): Carbon isotope evidence for the timing of the Cretaceous-Palaeogene macrobenthic colonization at the Agost
section (southeast Spain). Palaeogeography, Palaeoclimatology, Palaeoecology, 203: 65-72.
Signor, P.W., Lipps, J.H. (1982): Sampling bias, gradual extinction patterns and catastrophes in the fossil record. Geological
Society of America, Special Papers, 190: 291-296.
Smit, J. (1982): Extinction and evolution of planktonic
foraminifera after a major impact at the Cretaceous/Tertiay
boundary. Geological Society of America, Special Papers,
190: 329-352.
Smit, J. (1990): Asteroid impact, extinctions and the Cretaceous-Tertiary Boundary. Geologie en Mijnbouw, 69: 187204.
Smit, J., Hertogen J. (1980): An extraterrestrial event at the
Cretaceous-Tertiary boundary. Nature, 285: 198-200.
Smit, J., Romein, A.J.T. (1985): A sequence of events across
the Cretaceous-Tertiary boundary. Earth and Planetary Science Letters. 74: 155-170.
Thierstein, H. (1981): Late Cretaceous nannoplankton and the
change at the Cretaceous-Tertiary boundary. SEPM Special
Publication, 32: 355-394.
Usera, J., Molina, E., Montoya, P., Robles, F., Santisteban, C.
(2000): Límites entre Sistemas y Pisos en la provincia de Alicante. In: J.C. Cañaveras, M.A. García del Cura, A. Meléndez
(eds). Itinerarios Geológicos por la Provincia de Alicante y
limítrofes. 43-58, Diputación Provincial de Alicante.
Van Veen, G.W. (1969): Geological investigations in the region
West of Caravaca, South-Eastern Spain. Thesis, Univ. Amsterdam, 143 pp.
Vera, J.A. (1983): La Cordillera Bética. Las Zonas Externas
de las Cordilleras Béticas. In: Instituto Geológico y Minero
Español (ed.), Geología de España, Libro Jubilar J. M. Ríos,
2: 218-251.
Von Hillebrandt, A. (1974): Bioestratigrafía del Paleogeno
en el Sureste de España (Provincias de Murcia y Alicante).
Cuadernos de Geología, 5: 135-153.
Widmark, J.G.V., Speijer, R.P. (1997a): Benthic foraminiferal
faunas and trophic regimes at the terminal Cretaceous Tethyan seafloor. Palaios, 12: 354-371.
Widmark, J.G.V., Speijer, R.P. (1997b): Benthic foraminiferal
ecomarker species of the terminal Cretaceous (late Maastrichtian) deep-sea Tethys. Marine Micropaleontology, 31:
135-155.
Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
147
APENDIX
List of planktic and benthic foraminiferal species
cited in the text and figures.
Cretaceous planktic foraminifera:
Abathomphalus intermedius (Bolli, 1951)
Abathomphalus mayaroensis (Bolli, 1951)
Archaeoglobigerina blowi Pessagno, 1967
Archaeoglobigerina cretacea (d’Orbigny, 1840)
Contusotruncana contusa (Cushman, 1926)
Contusotruncana patelliformis (Gandolfi, 1955)
Contusotruncana walfischensis (Todd, 1970)
Globigerinelloides praeriehillensis Pessagno, 1967
Globigerinelloides rosebudensis Smith y Pessagno, 1973
Globigerinelloides subcarinatus (Brönnimann, 1952)
Globigerinelloides volutus (White, 1928)
Globigerinelloides yaucoensis (Pessagno, 1967)
Globotruncana aegyptiaca Nakkady, 1950
Globotruncana arca (Cushman, 1926)
Globotruncana mariei Banner y Blow, 1960
Globotruncana rosetta (Carsey, 1926)
Globotruncanita angulata (Tiev, 1951)
Globotruncanita conica (White, 1928)
Globotruncanita dupeublei (Caron, González Donoso, Robaszynski,Wonders,1984)
Globotruncanita falsocalcarata (Kerdany y Abdelsalam, 1969)
Globotruncanita fareedi (El Naggar, 1966)
Globotruncanita insignis (Gandolfi, 1955)
Globotruncanita stuarti (de Lapparent, 1918)
Globotruncanita stuartiformis (Dalbiez, 1955)
Globotruncanella caravacaensis Smit, 1982
Globotruncanella havanensis (Voorwijk, 1937)
Globotruncanella minuta Caron y González Donoso, 1984
Globotruncanella petaloidea (Gandolfi, 1955)
Globotruncanella pschadae (Keller, 1946)
Gublerina acuta de Klasz, 1953
Gublerina cuvillieri Kikoine, 1948
Guembelitria cretacea Cushman, 1933
Guembelitria trifolia (Morozova, 1961)
Hedbergella holmdelensis Olsson, 1964
Hedbergella monmouthensis (Olsson, 1960)
Heterohelix glabrans (Cushman, 1938)
Heterohelix globulosa (Ehrenberg, 1840)
Heterohelix labellosa Nederbragt, 1991
Heterohelix navarroensis (Loeblich, 1951)
Heterohelix planata (Cushman, 1938)
Heterohelix pulchra (Brotzen, 1936)
Heterohelix punctulata (Cushman, 1938)
Heterohelix postsemicostata (Vasilenko, 1961)
Planoglobulina acervulinoides (Egger, 1899)
Planoglobulina carseyae (Plummer, 1931)
Planoglobulina manuelensis (Martin, 1972)
Planoglobulina multicamerata (de Klasz, 1953)
Plummerita hantkeninoides (Brönnimann, 1952)
Pseudoguembelina costellifera Masters, 1976
Pseudoguembelina costulata (Cushman, 1938)
Pseudoguembelina excolata (Cushman, 1926)
Pseudoguembelina hariaensis Nederbragt, 1991
Pseudoguembelina kempensis Esker, 1968
Pseudoguembelina palpebra Brönnimann y Brown, 1953
Pseudotextularia elegans (Rzehak, 1891)
Pseudotextularia nuttali (Voorwijk, 1937)
Pseudotextularia intermedia de Klasz, 1953
Racemiguembelina fructicosa (Egger, 1899)
Racemiguembelina powelli Smith y Pessagno, 1973
Rugoglobigerina hexacamerata Brönnimann, 1952
Rugoglobigerina macrocephala Brönnimann, 1952
Rugoglobigerina milamensis Smith y Pessagno, 1973
Rugoglobigerina pennyi Brönnimann, 1952
Rugoglobigerina reicheli Brönnimann, 1952
Rugoglobigerina rotundata Brönnimann, 1952
Rugoglobigerina rugosa (Plummer, 1926)
Rugoglobigerina scotii (Brönnimann, 1952)
Schackoina multispinata (Cushman y Wickenden, 1930)
Paleogene planktic foraminifera:
Chiloguembelina morsei Kline (1943)
Chiloguembelina midwayensis (Cushman, 1940)
Eoglobigerina edita (Subbotina, 1953)
Eoglobigerina eobulloides (Morozova, 1959)
Eoglobigerina fringa (Subbotina, 1950)
Eoglobigerina microcellulosa (Morozova, 1961)
Eoglobigerina pentagona (Morozova, 1961)
Eoglobigerina polycamera (Khalilov, 1956)
Eoglobigerina praeedita Blow, 1979
Eoglobigerina simplicissima Blow (1979)
Eoglobigerina spiralis (Bolli, 1957)
Eoglobigerina tetragona Morozova (1961)
Eoglobigerina trivialis (Subbotina, 1953)
Globanomalina archeocompressa (Blow, 1979)
Globanomalina compressa (Plummer, 1926)
Globanomalina imitata (Subbotina, 1953)
Globanomalina planocompressa (Shutskaya, 1965)
Globoconusa alticonusa (Li, McGowran and Boersma, 1995)
Globoconusa daubjergensis (Brönnimann, 1953)
Globoconusa fodina (Blow, 1979)
Globoconusa cf. fringa (in Luterbacher and Premoli Silva, 1964)
Globoconusa minutula (Luterbacher and Premoli Silva, 1964)
Guembelitria alabamensis Liu y Olsson (1992)
Guembelitria irregularis Morozova (1961)
Parasubbotina moskvini (Shutskaya, 1953)
Parasubbotina pseudobulloides (Plummer, 1926)
Parasubbotina varianta (Subbotina, 1953)
Parvularugoglobigerina cf. hemisphaerica (in Blow, 1979)
Parvularugoglobigerina eugubina (Luterbacher and Premoli Silva, 1964)
Parvularugoglobigerina longiapertura (Blow, 1979)
Parvularugoglobigerina perexigua (Li, McGowran and Boersma, 1995)
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Molina et al. / Journal of Iberian Geology 31 (2004) 135-148
Parvularugoglobigerina sabina (Luterbacher and Premoli Silva, 1964)
Parvularugoglobigerina umbrica (Luterbacher and Premoli Silva, 1964)
Praemurica inconstans (Subbotina, 1953)
Praemurica pseudoinconstans (Blow, 1979)
Praemurica taurica (Morozova, 1961)
Subbotina triloculinoides (Plummer, 1926)
Woodringina claytonensis Loeblich and Tappan, 1957
Woodringina hornerstownensis Olsson, 1960
Cretaceous/Paleogene small benthic forminifera:
Bolivinoides delicatulus Cushman, 1927
Bolivinoides draco (Marsson, 1878)
Bulimina trinitatensis Cushman and Jarvis 1928
Cibicidoides ekblomi Brotzen 1948
Cibicidoides hyphalus (Fisher, 1969)
Cibicidoides velascoensis (Cushman, 1925)
Clavulinoides trilatera (Cushman, 1926)
Eouvigerina subsculptura McNeil and Caldwell, 1981
Gaudryina pyramidata Cushman, 1926
Glomospirella grzybowski Jurkiewicz, 1960
Loxostomum eleyi (Cushman, 1927)
Nuttallinella florealis (White, 1928)
Paralabamina lunata (Brotzen, 1948)
Praebulimina reussi (Morrow, 1934)
Pseudouvigerina plummerae Cushman, 1927
Pyramidina rudita (Cushman and Parker, 1936)
Repmanina charoides (Jones and Parker, 1860)
Sitella cushmani (Sandidge, 1932)
Spiroplectammina spectabilis (Grzybowski, 1898)
Stensioeina beccariiformis (White, 1928)